1. Field of the Invention
The present invention relates to an electric power steering apparatus.
2. Description of the Related Art
Electric power steering apparatuses in which a steering wheel is coupled to tires through a steering shaft are provided to reduce a steering force to be generated by a driver with an auxiliary torque, generated by an electric motor according to a magnitude of an applied steering torque. The auxiliary torque is transmitted to the steering shaft in addition to the steering force by the driver.
In automobiles having such an electric power steering apparatus, when a rotation direction of the steering wheel is switched, for example, when the steering wheel is rotated in a clockwise direction and then in a counterclockwise direction, because the steering shaft maintains the status up to now by inertia, the rotation direction cannot be changed immediately in the opposite direction. Accordingly, there is a problem of a delay in steering due to inertia of the steering shaft.
JP 2006-264621 A discloses an electric power steering apparatus including a rack shaft movable in a width direction of the vehicle, a rack housing for housing the rack shaft, first and second bearings installed between the rack shaft and the rack housing, and an elastic member, installed between the rack shaft and the rack housing, abutting the rack shaft and the rack housing. In this electric power steering apparatus, the elastic member suppresses vibrations in a radial direction of the rack shaft.
JP2003-19967 A discloses a steering apparatus for a vehicle having a steering wheel returning mechanism including a left lever and a right lever rotating with linkage with steering the steering wheel, a spring intervened between ends of the left and right levers, and a center stopper pin on which the other end of the left or the right lever abut. When the steering wheel is operated, the spring elongates until the other end of either of the left or the right lever abuts the center stop pin. After the operation of the steering wheel completes, when the steering direction of the steering wheel is switched, the steering wheel returns in the opposite direction by an amount of elongation of the spring. Accordingly, a detection value of a steering wheel angle detection unit can be equalized to a turning angle detection of steering wheels. This stops an unnecessary current flowing in the electric power steering unit to save energy.